Transformer



. Patented Feb. 20, 1951 TRANSFORMER Albert E. Feinberg, Chicago, 111., anig'nor to Advance Transformer 00., Chicago, 111., a eorporation of Illinois Application September 19, 1947, Serial No. 774,974

9 Claims- (Cl. 171-777) This invention relates to transformers for glow discharge devices, such as hot cathode fluorescent lamps, and this application is a continuation in part of my pending application, Serial No. 731,992, filed March 3, 1947, now abandoned.

In my pending application above referred to there is shown a. transformer for fluorescent tubes which is provided with a primary coil and two sets of series connected secondary coils. The secondaries are connected so that one of the secondary coils bucks the remainder of the secondary coils, the arrangement being such as to provide a high open circuit voltage and at the same time permit the obtainin of sufficient inductance in the secondary coils to limit the load current to the proper amount. It is one of the objects of the present invention to provide means for improving the power factor of a transformer unit of the above mentioned character. This result is accomplished, in the preferred embodiment of the present invention, by providing an auxiliary winding which is more closely coupled to the primary winding than the coupling between the primary and the load carrying secondaries, and which is connected in step-up auto transformer relationship to the primary. A condenser is connected across this auxiliary secondary winding to compensate for the lagging current of the rest of the load. The step-up auto transformer relationship of the auxiliary winding permits the use of a small size condenser to effect the necessary power factor correction. It is one of the objects of the present invention to provide a power factor cor- I recting transformer coil which is electrically in parallel relationship to the load carrying secondary cells that include a bucking coil in combination with boosting coils. As a result of the combination of the buckin and boosting coils in the load circuit it is found that when the lamp does not function the current drawn by the condenser in the step-up auto transformer circuit is of approximately the same value as when the lamp does function. Therefore there is no likelihood of overheating the apparatus.

The attaimnent of the above and further objects of the present invention will be apparent from the following specification taken in conjunction with the accompanying drawing forming a part thereof.

In the drawing:

Figure l is a diagrammatic view illustrating a preferred embodiment of the present invention; and

Figure 2 is a similar view illustrating another embodiment thereof.

Reference may now' be had more particularly to the drawing wherein like reference numerals designate like parts throushout.

' In Figure 1 there is shown a transformer I which includes a rectangular core on which are located the various. coils. The core itself is made of identical L-shaped laminations, indicated at 2, the long legs 3 of which are inserted through the coils in the usual manner. The transformer includes a single primary coil 4 and three load carrying secondary coils 5, 6 'and I which are connected in series with one another and in step-up auto transformer relationship with the primary coil 4. The three coils I, 6 and I together onstitute the load carrying secondary. The coils B and 6 are connected so that their voltages are cumulative, that is, in such a manner that the voltages generated therein are in the same direction at any given instant, and the coil I is connected so that its voltage bucks the voltage of the coils 5 and 6. The conductor I3 from the load carrying secondary is connected to one end of a cathode heating filament I4 of a hot cathode glow discharge tube I5, for instance, a conventional fluorescent lamp. Another cathode heating filament I6 of the glow discharge tube is connected in series with the filament I4 by way of a usual starter switch I8. The other end of the filament I s is connected to a conductor III of a power line I9-20 which represents a source of 115-120 volt 60 cycle current. The starter I8 is of the manual or automatically operated type and connects the filaments in series during startin and is adapted to open the circuit a number of seconds after the filament circuit has been completed, thereby allowing a time interval for the cathodes to become sufllciently hot for the establishment of an are or discharge between them. The primary 4 is connected directly across the power line I9--2II.

The transformer I is provided with a power factor correcting secondary coil 25. This coil is concentric with the primary coil 4 and preferably of substantially the same number of turns as the primary coil 4 and of the same size wire.

The secondary 25 is connected in step-up autotransformer relationship with the primary 4. and supplies current to a power factor correcting condenser 26.

necessary power factor correction. Because of,

the presence of'the bucking coil 8 in opposition to the sum of the line voltage and the voltage of the 'coils and 8 the current in the primary coil does not increase excessively when. the starter switch I8 is short circuited. As a result it is possible to use a smaller diameter wire for the primary than was heretofore possible, or to use more primary turns on one coil without danger of the coil becoming excessively warm. The current drawn by the condenser is of approximately the same value when the lamp does not function, as during normal operation of the lamp, and there is no danger of overheating under these circumstances. In one preferred construction the primary coll I was wound on top of the power factor correcting coil 25, the two coil unit consisting of a single winding of approximately 3700 turns tapped at the mid layer. The bucking coil 1 was of 700 turns and the coils 5 and 6 were each of 800 turns. The coils 5 and 6 were placed approximately one inch from the coils I and the two coil unit 425. The laminations of the transformer l/were formed of L-shaped laminations, the long leg being six inches long and the short leg one-half inch long, and were stacked to a thickness of flve-eighths of an inch. The condenser was rated at 3 mcf. at 200 volts 60 cycles. Such an arrangement was found to give a good power factor and good voltage and current characteristics during starting and operating conditions as well as during non-operative conditions of the lamp i5.

In Figure 2 there is shown an alternate arrangement which differs from the arrangement previously described only in that the primary coil is divided into two parts 4a and lb, connected in series, and the power factor correcting coil is also divided into two parts 25a and 25b, also connected in series, the parts to, to, 25a and 25b being each of the same number of turns and the parts 25a and 25b surrounding the parts la and 4b, respectively. The secondary in this instance consists of the two coils i and 8 that areconnccted so that their voltages are always in'the same direction and connected in series with two buckling coilsla and lb which together correspond functionally to the single bucking coil 1 previously described. The four coils I, 0, la and lb are connected in series and in step-up auto transformer relationship with the primary and the combined number of turns on the coils la and lb is slightly less than the number of turns on the coil 5 or the coil 8.

In each of the above embodiments it is to be noted that the power factor correcting coils are more closely coupled with the primary coils and have a lower leakage reactance therewith than in the case of any of the secondary load current carryingcoils. Itisalsotobenotedthatofthe coils constituting the load currentcarrying secondaries the bucking coil is in each instance more closely coupled with the primary and has a lower leakage reactance therewith than in the case of the other two load current carrying secondary coils. The current in the bucking coil 1 (or the coils In or 122) is at every instant in such directionastoproduceailuxinphase withthemagnetizing flux of the magnetizin current in the coil 4. Therefore, the effective self-inductance of the bucking coil I (or the bucking coils Ia-1b) is increased.

Whiiethebuckingcoil'lofl'igure lisshown as being physically separate from the primary coil 4, it is within the purview of the present invention to wind the coil I concentric with the coil In some instances this may be desirable especially if the power factor correcting coil 2| is omitted. In most instances, however, I have found that it is more desirable to locate the bucking coil 1 separate from the coil 4- because of the space requirements of the transformer core and because it is desirable that the coil 1 be of wire of diflerent diameter than the wire of the coil 4. However, in those instances where these are not important factors the coil 1 may be wound concentric with the coil 4, the connections being such as to maintain the direction of now of current in the bucking coil at every instance in such a direction as to produce a flux in phase with the magnetizing flux in the primary coil 4.

In compliance with the requirements of the patent statutes I have here shown and described a few preferred embodiments of my invention. It is, however, to be understood that the invention is not limited to the precise constructions here shown, the same being merely illustrative of the principles of the invention. What I consider new and desire to secure by Letters Patent is:

1. A transformer for operating an electric discharge device, said transformer comprising an elongated core, a primary coil on said core, series connected secondary turns on the core a minority of the secondary turns being connected with their induced voltage in opposition to the induced voltage of the remaining secondary turns, the secondary turns being connected to the primary in step-up auto transformer relationship, and a power factor correcting secondary on said core and also connected in step-up auto transformer relationship with the primary all of the turns of the power factor correcting secondary being electrically separate from the first mentioned series connected secondary turns.

2. A transformer for operating an electric discharge device, said transformer comprising an elongated core, a primary coil on said core, series connected secondary turns on the core a minority' of the secondary turns being connected with their induced voltage in opposition to the induced voltage of the remaining secondary turns, the secondary turns being connected to the primary in step-up auto transformer relationship, and a power factor correcting secondary on said core and also connected in step-up auto transformer relationship with the primary, said power factor correcting secondary bein concentric with the primary all of the turns of the power factor correcting secondary being electrically separate from the first mentioned series connected secondary turns.

3. A transformer for operating an electric discharge device, said transformer comprisin an elongated core. a primary coil on said core, series connected secondary turns on the core a minority of the secondary turns being connected with their induced voltage in opposition to the induced voltage of the remaining secondary turns, the secondary turns being connected to the primary in step-up auto transformer relationship, and a power factor correcting secondary on said core and also connected in step-up auto transformer relationship with the primary, said power factor correcting secondary being concentric with the primary and of substantially the same number of turns as the primary.

4. A transformer for operating an electric glow discharge device comprising a magnetic core having primary coil turns thereon and secondary coil turns thereon, the secondary coil turns being in series and connected in step-up .auto transformer relation with the primary coil,

a minority of the secondary coil turns being connected in voltage bucking relationship with the remaining series connected turns, said minority coils being more closely coupled with and having a lower leakage reactance with the primary turns than do the remaining secondary turns, and a power factor correcting secondary coil in addition to the first mentioned secondary coil turns.

5. A transformer for operating an electric glow discharge device comprising a magnetic core havin primary coil turns thereon and secondary coil turns thereon, the secondary coil turns being in series and connected in step-up auto transformer relation with the primary coil, a minority of the secondary coil turns being connected in voltage bucking relationship with the remaining series connected turns, said minority coils being more closely coupled with and having a lower leakage reactance with the primary turns than do the remaining secondary turns, and a power factor correcting secondary coil in addition to the first mentioned secondary coil turns, said power factor correcting secondary being connected in step-up auto transformer relation with the primary coil turns and more closely coupled thereto than the coupling between said minority secondary turns and the primary coil turns. I

6. A transformer for operating an electric glow discharge device comprising a magnetic core having primary coil turns thereon and secondary coil turns thereon, the secondary coil turns being in series and connected in step-up auto transformer relation with the primary coil,

a minority of the secondary coil turns being con- 7, A transformer for operating an electric glow discharge device comprising an elongated core having parallel side legs, a primary coil on one of the legs adjacent one end thereof, a secondary coil on the same leg at the opposite end thereof, two additional secondary coils both located on the other leg, all three secondary coils being connected in series and in step-up auto transformer relationship with the primary coil, that one of the secondaries which has the lowest leakage reactance with the primary being in opposition to the other two secondaries, and a power factor correcting secondary coil concentrio with the primary and of substantially the same number of turns as the primary. 4

8. A transformer for operating an electric discharge device comprising an elongated core having parallel side legs, a primary coil on the core adjacent one end thereof, a pair of secondary coils adjacent the opposite end of the core and on the respective legs thereof, an additional secondary coil on the core at the first mentioned end thereof and located adjacent the primary coil, said additional secondary coil being of fewer turns than the sum of the turns on said first mentioned secondary coils and connected in series opposition therewith, the primary coil and the series connected secondary coils being connected in step-up auto transformer relationship, and a power factor correcting secondary coil in addition to the previously mentioned coils, said power factor correcting secondary coil being connected in step-up auto transformer relation with the primary coil.

9. A transformer for operating an electric glow discharge device comprising an elongated core having parallel side legs, a primary coil on one of the legs adjacent one end thereof, a secondary coil on the same leg at the opposite end thereof, and two additional secondary coils both located on the other leg, all three secondary coils being connected in series and in step-up auto transformer relationship with the primary coil, that one of the secondaries which has the lowest 5 leakage reactance with the primary being in op- The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,950,396 Boucher Mar. 13, 1934 2,212,198 Sola Aug. 20, 1940 2,461,029 Boucher Feb. 8, 1949 

